Oral care composition

ABSTRACT

An oral care composition is disclosed comprising calcium silicate and high refractive index composite particles, wherein the refractive index of the composite particles is in the range from 1.9 to 4.0, and wherein the calcium silicate and high refractive index composite particles are present at a calcium silicate to composite particles weight ratio of 1:10 to 2:1.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to oral care compositions such as toothpastes, gums, mouthwashes and the like. In particular the presentinvention relates to oral care compositions containing a particulatetooth whitening agent. The invention also relates to the use of suchcompositions for whitening and/or remineralizing of teeth of anindividual.

BACKGROUND OF THE INVENTION

The enamel layer of the tooth is naturally an opaque white or slightlyoff-white colour. However, this enamel layer can become stained ordiscoloured. The enamel layer of the tooth is composed of hydroxyapatitemineral crystals that create a somewhat porous surface. It is believedthat this porous nature of the enamel layer allows staining agents anddiscolouring substances to permeate the enamel and discolour the tooth.

Many products we consume have a negative impact on our teeth and mouth.Many substances can stain or reduce the whiteness of one's teeth, inparticular, certain foods, tobacco products, and fluids such as tea andcoffee. These staining and discolouring substances are often able topermeate the enamel layer. This problem occurs gradually over manyyears, but imparts a noticeable discoloration of the enamel of one'steeth.

Consumers have always had a strong desire for white teeth and manyindividuals are dissatisfied with their current teeth colour. Thisdesire for whiter teeth has given rise to a growing trend in theincreased use of tooth whitening products.

A variety of products are currently used for teeth whitening. Suchproducts often comprise peroxides, abrasives or both in order to cleanand whiten teeth. These types of products are often not desired sincethey do not contribute to the remineralization of teeth and can causedamage to teeth and gums if overused. Products comprising calcium sourcehave been developed in an attempt to enhance the characteristics ofteeth. Such products, however, do not positively adhere to teeth andthereby may only contact teeth for a brief period of time prior to beingrinsed out of the mouth in wash water.

The present inventors have now recognized a need to develop an oral careproduct which has tooth whitening agents that are suitable to adhere tothe surface of teeth for a long enough period of time to provide notonly instant but also long-lasting whitening benefits to teeth. It hasbeen found that calcium silicate, especially calcium silicate in theform of a hydrate can behave as a deposition aid and unexpectedlyenhances the deposition of particulate tooth whitening agent on toothsurfaces which delivers both instant and excellent long-lasting toothwhitening benefits.

Additional Information

WO 2008/068149 A (Unilever) discloses an oral care product comprising afirst composition comprising an insoluble calcium salt that is not acalcium phosphate salt, a second independent composition comprising asource of phosphate ions, and a means for delivering each of thecompositions to the surface of the teeth. The preferred insolublecalcium salt is calcium silicate.

WO 2008/015117 A (Unilever) discloses a calcium oxide-silica compositebiomaterial either in amorphous state or crystalline state having anaverage pore size, as determined by the BET method, in the range of from0.8 to 4 nm, wherein the calcium oxide-silica content of the biomaterialis at least 80 wt percent, the balance being optionally one or moreother materials and wherein the molar ratio of calcium oxide to silicais at least 0.1.

WO 2012/031785 A (Unilever) discloses composite particle activessuitable for use in oral care compositions. The composite particleactives have a core and a coating whereby the coating interacts withphosphate ions to produce calcium and phosphate reaction products thatare suitable to adhere to tooth enamel and/or dentin in order to improvecharacteristics of teeth.

WO 2012/031786 A (Unilever) discloses oral care compositions withcomposite particle actives described in WO 2012/031785 A (Unilever).

None of the additional information above describes an oral carecomposition comprising calcium silicate, particularly calcium silicatehydrate as a deposition aid which enhances the deposition of particulatewhitening agents on teeth surface in order to achieve excellent instantand long-lasting tooth whitening results.

Tests And Definitions

Dentifrice

“Dentifrice” for the purposes of the present invention means a paste,powder, liquid, gum or other preparation for cleaning the teeth or othersurfaces in the oral cavity.

Tooth Paste

“Tooth paste” for the purpose of the present invention means a paste orgel dentifrice for use with a toothbrush. Especially preferred are toothpastes suitable for cleaning teeth by brushing for about two minutes.

Mouth Wash

“Mouth wash” for the purpose of the present invention means liquiddentifrice for use in rinsing the mouth. Especially preferred are mouthwashes suitable for rinsing the mouth by swishing and/or gargling forabout half a minute before expectorating.

Particle Size

“Particle size”, as used herein, refers to particle diameter unlessotherwise stated. Diameter is meant to mean the largest measurabledistance on a particle in the event a well-defined sphere is notgenerated. Particle size can be measured, for example, by dynamic lightscattering (DLS).

Composite Particle

“Composite particle”, as used herein, refers to a particle comprising afirst component core and a second component coating wherein the core andcoating are composed of different materials.

Refractive Index

Refractive index is quoted at a temperature of 25° C. and a wavelengthof 589 nm.

pH

pH is quoted at atmospheric pressure and a temperature of 25° C. Whenreferring to the pH of an oral care composition, this means the pHmeasured when 5 parts by weight of the composition is uniformlydispersed and/or dissolved in 20 parts by weight pure water at 25° C. Inparticular the pH may be measured by manually mixing 5 g oral carecomposition with 20 mL water for 30 s, then immediately testing the pHwith indicator or a pH meter.

Solubility

“Soluble” and “insoluble”, as used herein, refers to the solubility of asource (e.g., like calcium salts) in water at 25° C. and atmosphericpressure. “Soluble” means a source that dissolves in water to give asolution with a concentration of at least 0.1 moles per litre.“Insoluble” means a source that dissolves in water to give a solutionwith a concentration of less than 0.001 moles per litre. “Sparinglysoluble”, therefore, is defined to mean a source that dissolves in waterto give a solution with a concentration of greater than 0.001 moles perlitre and less than 0.1 moles per litre.

Water of Hydration

“Water of hydration”, as used herein, refers to water chemicallycombined with a substance in a way that it can be removed by heatingwithout substantially changing the chemical composition of thesubstance. In particular, water which could only be removed when heatedabove 200° C. The water loss is measured using thermo gravimetricanalysis (TGA) with a Netzsch TG instrument. The TGA is conducted underan N₂ atmosphere with heating rate of 10 degree/min in the range of 30to 900° C.

Substantially Free

“Substantially free of”, as used herein, means less than 1.5%, andpreferably less than 1.0%, and more preferably less than 0.75% and morepreferably still less than 0.5%, and even more preferably less than 0.1%and most preferably from 0.0 to 0.01% by weight, based on total weightof the oral care composition, including all ranges subsumed therein.

Viscosity

Viscosity of a tooth paste is the value taken at room temperature (25°C.) with a Brookfield Viscometer, Spindle No.4 and at a speed of 5 rpm.Values are quoted in centipoises (cP=mPa·S) unless otherwise specified.

Remineralization

“Remineralization”, as used herein, means in situ (i.e. in the oralcavity) generation of calcium phosphate on teeth (including layers onteeth from 10 nm to 20 microns, and preferably from 75 nm to 10 microns,and most preferably, from 150 nm to 5 microns thick including all rangessubsumed therein) to reduce the likelihood of tooth sensitivity, toothdecay, regenerate enamel and/or improve the appearance of teeth bywhitening through the generation of such new calcium phosphate.

Miscellaneous

Except in the examples, or where otherwise explicitly indicated, allnumbers in this description indicating amounts of material or conditionsof reaction, physical properties of materials and/or use may optionallybe understood as modified by the word “about”.

All amounts are by weight of the final oral care composition, unlessotherwise specified.

It should be noted that in specifying any ranges of values, anyparticular upper value can be associated with any particular lowervalue.

For the avoidance of doubt, the word “comprising” is intended to mean“including” but not necessarily “consisting of” or “composed of”. Inother words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered tocover all embodiments as found in the claims as being multiply dependentupon each other irrespective of the fact that claims may be foundwithout multiple dependency or redundancy.

Where a feature is disclosed with respect to a particular aspect of theinvention (for example a composition of the invention), such disclosureis also to be considered to apply to any other aspect of the invention(for example a method of the invention) mutatis mutandis.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is directed to an oral carecomposition comprising:

-   -   a) calcium silicate; and    -   b) high refractive index composite particles    -   wherein the calcium silicate and high refractive index composite        particles are present in a weight ratio (a:b) of 1:10 to 2:1.

In a second aspect, the present invention is directed to a packaged oralcare product comprising the oral care composition of the first aspect ofthis invention.

In a third aspect, the present invention is directed to a process formanufacturing any embodiment of the oral care composition of the firstembodiment comprising the steps of:

-   -   i) manufacturing high refractive index composite particles;    -   ii) mixing the composite particles with calcium silicate to form        the oral care composition.

In a fourth aspect, the present invention is directed to a method forproviding tooth whitening benefits by using oral care composition of thefirst aspect of this invention.

All other aspects of the present invention will more readily becomeapparent upon considering the detailed description and examples whichfollow.

DETAILED DESCRIPTION

Now it has been found that the presence of calcium silicate especiallycalcium silicate in the form of a hydrate can behave as a deposition aidand unexpectedly enhances the deposition of particulate tooth whiteningagent such as high refractive index composite particles on teethsurfaces which delivers not only instant but also excellent long-lastingwhitening benefits.

The term “deposition aid” in the context of the present inventiongenerally means a material which aids deposition of the particulatetooth whitening agent from the continuous phase of the composition ontothe tooth surface during use of the composition.

Calcium Silicate

In a preferred embodiment, the calcium silicate used is CaSiO₃ which haslow water solubility and is made commercially available under the nameSorbosil CA40 by PQ. In another preferred embodiment, the calciumsilicate is insoluble, present as the composite material calciumoxide-silica (CaO—SiO₂), which is described, for example, ininternational patent application published as WO 2008/01517(Unilever)which is hereby incorporated by reference in its entirety. For a calciumsilicate composite material, the atom ratio of calcium to silicon(Ca:Si) may be from 1:10 to 3:1. The Ca:Si ratio is preferably 1:5 to2:1, and more preferably, from 1:3 to 2:1, and most preferably, fromabout 1:2 to 2:1. The calcium silicate may comprise mono-calciumsilicate, bi-calcium silicate, or tri-calcium silicate. The calciumsilicate may be in a crystalline or amorphous state or even in amesoporous state.

In addition to calcium oxide, silica, the particles comprising thecalcium silicate which is not hydrated may comprise other components,such as metal cations, anions (such as phosphate) and the like. However,it is preferred that the particles comprise calcium oxide, silica in anamount of at least 70% by weight of the particles, more preferably atleast 80%, more preferably still at least 90% and even more preferablyat least 95%. Most preferably the particles consist of (or at leastconsist essentially of) calcium oxide, silica.

In an especially preferred embodiment, the calcium silicate is calciumsilicate hydrate. The calcium silicate hydrate for use in the presentinvention comprises at least calcium oxide (CaO), silica (SiO₂) andwater. Compared with conventional calcium silicate which are nothydrated, the calcium silicate hydrate comprises the water of hydrationin an amount of at least 5% by weight of the calcium silicate hydrate,preferably at least 10%, more preferably at least 15%, even morepreferably at least 20% and most preferably at least 25%. The watercontent is typically no greater than 50% by weight of the calciumsilicate hydrate, more preferably no greater than 40%, even morepreferably no greater than 35% and most preferably no greater than 30%.

The calcium silicate hydrate preferably comprises at least 20% silica byweight of the calcium silicate hydrate, more preferably at least 30%,more preferably still at least 40% and most preferably at least 55%. Thesilica content is preferably no greater than 70% by weight of thecalcium silicate hydrate, more preferably no greater than 65% and mostpreferably no greater than 60%.

To provide calcium necessary for remineralization, the calcium silicatehydrate preferably comprises calcium oxide in an amount of at least 5%by weight of the calcium silicate hydrate, more preferably at least 7%,more preferably still at least 10%, even more preferably at least 12%and most preferably at least 15%. The calcium oxide content is typicallyno greater than 50% by weight of the calcium silicate hydrate, morepreferably no greater than 40%, even more preferably no greater than 30%and most preferably no greater than 25%.

The calcium silicate hydrate preferably comprises Ca and Si in an atomratio (Ca:Si) less than 1:1, more preferably less than 1:1.2, morepreferably still from 1:1.5 to 1:4 and most preferably from 1:1.7 to1:3.

The calcium silicate may be amorphous or at least partly crystalline ormesoporous. The calcium silicate is preferably particulate as thisallows for maximum surface area for contact with dental tissue. Thuspreferably the composition comprises particles comprising the calciumsilicate. More preferably the particles have a weight average particlesize of five microns or less, and even more preferably from 10 to 100%,and especially, from 25 to 100%, and most especially, from 70% to 100%by weight of the particles comprising calcium silicate used in thisinvention have a particle size from 0.1 to 1.5 microns.

In addition to calcium oxide, silica and water, the particles whichcomprise the calcium silicate hydrate may comprise other components,such as metal cations, anions (such as phosphate) and the like. However,it is preferred that the particles comprise CaO, SiO₂ and water in anamount of at least 70% by weight of the particles, more preferably atleast 80%, more preferably still at least 90% and even more preferablyat least 95%. Most preferably the particles consist of (or at leastconsist essentially of) CaO, SiO₂ and water.

Typically, the oral care composition of the present invention comprisesfrom 0.1 to 50% by weight of the calcium silicate, more preferably from0.2 to 30%, most preferably from 1 to 20%, based on the total weight ofthe oral care composition and including all ranges subsumed therein.

Composite Particles

The only limitation with respect to the composite particle that may beused in this invention is that the same is suitable for use in themouth.

It is known that the refractive index of a particle comprising more thanone material can be calculated based on the refractive indices andvolume fractions of the constituents using effective medium theory, asis described for example in WO 2009/023353. In order to provideexcellent whitening effect, the composite particles of the presentinvention is preferred to have a high refractive index of at least 1.9,more preferably at least 2.0, even more preferably at least 2.2, evenmore preferably still at least 2.4 and most preferably at least 2.5. Themaximum refractive index of the composite particles is not particularlylimited but preferably up to 4.0.

The composite particle comprises a first component core and a secondcomponent coating. Typically, the core of the composite particlecomprises a material suitable to physically and immediately improvecharacteristics of teeth and especially whiten teeth. Particularsuitable materials are metal salts and preferred are salts where themetal is selected from zinc (Zn), titanium (Ti), zirconium (Zr) or acombination thereof. Preferably, the metal salts is (or at leastcomprises) a metal oxide such as titanium dioxide (TiO₂), zinc oxide(ZnO), zirconium dioxide (ZrO₂) or a combination thereof. In addition,the core of the composite particle can also comprise non-metal oxidessuch as silicon monoxide (SiO).

The core of the composite particle typically makes up from 3 to 98%, andpreferably from 6 to 65%, and most preferably from 10 to 55% by weightof the composite particle, based on total weight of the compositeparticle and including all ranges subsumed therein. In a preferredembodiment, the core comprises metal oxides, non-metal oxides or acombination thereof in an amount of at least 50% by weight of the coreand more preferably at least 70%, more preferably still from 80 to 100%and most preferably from 85 to 95%. In an especially preferredembodiment, the core is at least 50% by weight titanium dioxide, andmost preferably, from 60 to 100% by weight titanium dioxide, based ontotal weight of the first component core.

The second component coating comprises material suitable to adhere totooth enamel, dentin or both. Typically the coating material comprisesthe element calcium, and optionally, other metals like potassium,sodium, aluminium, magnesium as well as mixtures thereof whereby suchoptional metals are provided as, for example, sulphates, lactates,oxides, carbonates or silicates. Optionally, the coating material may bealuminium oxide or silica. In a preferred embodiment, the coatingmaterial is suitable to provide a biological or chemical improvement toteeth which is long term (e.g., results in hydroxyapatite formation).Preferably, the coating employed comprises at least 50% by weightelemental calcium, and most preferably, at least 65% by weight elementalcalcium based on total weight of metal in the coating. In an especiallypreferred embodiment, the metal in the coating is from 80 to 100% byweight of elemental calcium, based on total weight of metal in thesecond component coating and including all ranges subsumed therein. Inanother especially preferred embodiment, the core and the coating areslightly soluble or insoluble in water, but most preferably, insolublein water.

Usually, at least 30% of the outer surface area of the first componentcore is coated with the second component coating, preferably at least50% of the core is coated with coating, most preferably, from 70 to 100%of the outer surface area of the first component core is coated with thesecond component coating.

The diameter of the composite particle is often from 10 nm to less than50 microns, and preferably, from 75 nm to less than 10 microns. In anespecially preferred embodiment, the diameter of composite particleactive is from 100 nm to 5 microns, including all ranges subsumedtherein. In yet another especially preferred embodiment, at least 40%,and preferably, at least 60%, and most preferably, from 75 to 99.5% ofthe diameter of the composite particle is the result of core, includingall ranges subsumed therein.

Typically, the oral care composition of the present invention comprisesfrom 0.25 to 60%, and preferably, from 0.5 to 40%, and most preferably,from 1 to 30% by weight of the composite particles, based on the totalweight of the oral care composition and including all ranges subsumedtherein.

In an especially desired embodiment, the second component coating cancomprise, for example, calcium phosphate, calcium gluconate, calciumoxide, calcium lactate, calcium carbonate, calcium hydroxide, calciumsulphate, calcium carboxymethyl cellulose, calcium alginate, calciumslats of citric acid, calcium silicate, mixture of thereof or the like.In another desired embodiment, the calcium source in the coating willcomprise calcium silicate. These compounds are also suitable to includeas reagents for calcium sources when making the composite particles ofthis invention. Similar salts with sodium, magnesium, aluminium andpotassium in lieu of calcium may, for example, be used as reagents toprovide the anionic portion of the second component coating duringparticle manufacturing.

In yet, another preferred embodiment, the coating can comprise theelement calcium which originates from insoluble calcium silicate,present as the composite material calcium oxide-silica (CaO—SiO₂) asdescribed in international patent applications published as WO2008/015117 and WO 2008/068248.

When a calcium silicate composite material is employed as coating, theratio of calcium to silicon (Ca:Si) may be from 1:10 to 3:1. The Ca:Siratio is preferably from 1:5 to 2:1, and more preferably, from 1:3 to2:1, and most preferably, from about 1:2 to 2:1. The calcium silicatemay comprise mono-calcium silicate, bi-calcium silicate, or tri-calciumsilicate whereby ratios of calcium to silicon (Ca:Si) should beunderstood to be atom ratios.

The preferred material employed in this invention to deliver calcium andgenerate second component coating on the composite particle may be in acrystalline or amorphous state. In an often preferred embodiment, thematerial to deliver calcium for the coating is in a mesoporous state,i.e. the source is a material having pores with diameters from 1 nm to 1micron. Mesoporous calcium silicate (MCS) is often preferred.

The MCS which may be used in second component coating in this inventioncan be made by combining a calcium salt (e.g., calcium chloride, calciumcarbonate, calcium hydroxide), a silica precursor like silicate (e.g.,sodium silicate, potassium silicate, tetraethyl orthosilicate ortetraethyl silicate)and a structure-directing agent to yield a solidsuitable for calcinating. A more detailed description of the processthat may be conducted to make the MCS suitable for use in this inventionis described in the aforementioned international patent applicationpublished as WO 2008/015117.

In an often desired embodiment, coating may be formed from CaO—SiO₂.

The present inventors have found that excellent whitening performancecan be achievable even when the calcium silicate is not used in greatexcess. Relative weight ratio of calcium silicate to high refractiveindex composite particles may range from 1:10 to 4:1, preferably from1:5 to 3:1, most preferably from 1:3 to 2:1.

Optional Components

The composite particles of the present invention may be capable ofadhering to tooth surfaces in the presence of calcium silicate evenwithout inclusion of a phosphate source in the oral care compositionitself. Without wishing to be bound by theory the present inventorsbelieve that this may be because the calcium silicate in the oralcomposition of the present invention reacts with phosphate ions insaliva and/or Si—OH groups may have an affinity for Ca ions in teeth.The remineralisation of calcium silicate around the composite particleshelps the deposition of composite particles on tooth surface byenhancing their resistance to shear force.

Thus in one embodiment the oral care composition may be substantiallyfree of phosphate source. This is especially preferred when thecomposition is a monophase hydrous composition (i.e. comprises greaterthan 1.5% water, preferably greater than 5% water, more preferablygreater than 10% water and most preferably from 20 to 90% water byweight of the composition). Presence of calcium silicate, compositeparticles and phosphate sources in a monophase hydrous formulation canlead to premature reaction of the calcium and phosphate and instabilityof the product.

For certain compositions, especially anhydrous compositions (i.e.compositions substantially free from water) or dual phase hydrouscompositions, it is preferable to compound a phosphate source in theoral composition to aid in situ generation of calcium phosphate.

The phosphate source that may be used in this invention is limited onlyto the extent that the same may be used in a composition suitable foruse in the mouth. Illustrative examples of the types of phosphate sourcesuitable for use in this invention include trisodium phosphate,monosodium dihydrogen phosphate, disodium hydrogen phosphate, sodiumpyrophosphate, tetrasodium pyrophosphate, sodium hexametaphosphate,tripotassium phosphate, monopotassium dihydrogen phosphate, dipotassiumhydrogen phosphate, mixtures thereof or the like. The phosphate sourceis preferably one which is water soluble.

When used, the phosphate source typically makes up from 0.5 to 22%, andpreferably, from 2 to 18%, and most preferably, from 4 to 16% by weightof the oral care composition, based on total weight of the oral carecomposition and including all ranges subsumed therein. In a preferredembodiment, the phosphate source used is trisodium phosphate andmonosodium dihydrogen phosphate at a trisodium phosphate to monosodiumdihydrogen phosphate weight ratio of 1:4 to 4:1, preferably 1:3 to 3:1,and most preferably, from 1:2 to 2:1, including all ratios subsumedtherein. In another preferred embodiment, the phosphate source used isor at least comprises monosodium dihydrogen phosphate.

The oral care composition preferably has a pH of greater than 5.0. Ifthe pH of the composition is too low then it may lower the pH in theoral cavity such that generation of in situ calcium phosphate isretarded. Therefore, it is preferred that the pH of the oral carecomposition is in the range 5.5 to 11.0, more preferably 6.0 to 10.5 andmost preferably 7.0 to 10.0.

The composition of the present invention is an oral care composition andtypically comprises physiologically acceptable carrier. The carrierpreferably comprises at least surfactant, thickener, humectant or acombination thereof.

Preferably the oral care composition comprises a surfactant. Preferablythe composition comprises at least 0.01% surfactant by weight of thecomposition, more preferably at least 0.1% and most preferably from 0.5to 7%. Suitable surfactants include anionic surfactants, such as thesodium, magnesium, ammonium or ethanolamine salts of C₈ to C₁₈ alkylsulphates (for example sodium lauryl sulphate), C₈ to C₁₈ alkylsulphosuccinates (for example dioctyl sodium sulphosuccinate), C₈ to C₁₈alkyl sulphoacetates (such as sodium lauryl sulphoacetate), C₈ to C₁₈alkyl sarcosinates (such as sodium lauryl sarcosinate), C₈ to C₁₈ alkylphosphates (which can optionally comprise up to 10 ethylene oxide and/orpropylene oxide units) and sulphated monoglycerides. Other suitablesurfactants include nonionic surfactants, such as optionallypolyethoxylated fatty acid sorbitan esters, ethoxylated fatty acids,esters of polyethylene glycol, ethoxylates of fatty acid monoglyceridesand diglycerides, and ethylene oxide/propylene oxide block polymers.Other suitable surfactants include amphoteric surfactants, such asbetaines or sulphobetaines. Mixtures of any of the above describedmaterials may also be used. More preferably the surfactant comprises oris anionic surfactant. The preferred anionic surfactants are sodiumlauryl sulphate and/or sodium dodecylbenzene sulfonate. Most preferablythe surfactant is sodium lauryl sulphate.

Thickener may also be used in this invention and is limited only to theextent that the same may be added to a composition suitable for use inthe mouth. Illustrative examples of the types of thickeners that may beused in this invention include, sodium carboxymethyl cellulose (SCMC),hydroxyl ethyl cellulose, methyl cellulose, ethyl cellulose, gumtragacanth, gum arabic, gum karaya, sodium alginate, carrageenan, guar,xanthan gum, Irish moss, starch, modified starch, silica basedthickeners including silica aerogels, magnesium aluminum silicate (e.g.,Veegum), Carbomers (cross-linked acrylates) and mixtures thereof.

Typically, sodium carboxymethyl cellulose and/or a Carbomer is/arepreferred. When a Carbomer is employed, those having a weight-averagemolecular weight of at least 700,000 are desired, and preferably, thosehaving a molecular weight of at least 1,200,000, and most preferably,those having a molecular weight of at least about 2,500,000 are desired.Mixtures of Carbomers may also be used herein.

In an especially preferred embodiment, the Carbomer is Synthalen PNC,Synthalen KP or a mixture thereof. It has been described as a highmolecular weight and cross-linked polyacrylic acid and identified viaCAS number 9063-87-0. These types of materials are availablecommercially from suppliers like Sigma.

In another especially preferred embodiment, the sodium carboxymethylcellulose (SCMC) used is SCMC 9H. It has been described as a sodium saltof a cellulose derivative with carboxymethyl groups bound to hydroxygroups of glucopyranose backbone monomers and identified via CAS number9004-32-4. The same is available from suppliers like Alfa Chem.

Thickener typically makes up from 0.01 to about 10%, more preferablyfrom 0.1 to 9%, and most preferably, from 1.5 to 8% by weight of theoral care composition, based on total weight of the composition andincluding all ranges subsumed therein.

When the oral care composition of this invention is a toothpaste or gel,the same typically has a viscosity from about 30,000 to 180,000centipoise, and preferably, from 60,000 to 170,000 centipoise, and mostpreferably, from 65,000 to 165,000 centipoise.

Suitable humectants are preferably used in the oral care composition ofthe present invention and they include, for example, glycerin, sorbitol,propylene glycol, dipropylene glycol, diglycerol, triacetin, mineraloil, polyethylene glycol (preferably, PEG-400), alkane diols like butanediol and hexanediol, ethanol, pentylene glycol, or a mixture thereof.Glycerin, polyethylene glycol, sorbitol or mixtures thereof are thepreferred humectants.

The humectant may be present in the range of from 10 to 90% by weight ofthe oral care composition. More preferably, the carrier humectant makesup from 25 to 80%, and most preferably, from 45 to 70% by weight of thecomposition, based on total weight of the composition and including allranges subsumed therein.

The oral care composition of the present invention may contain a varietyof other ingredients which are common in the art to enhance physicalproperties and performance. These ingredients include antimicrobialagents, anti-inflammatory agents, anti-caries agents, plaque buffers,fluoride sources, vitamins, plant extracts, desensitizing agents,anti-calculus agents, biomolecules, flavors, proteinaceous materials,preservatives, opacifying agents, coloring agents, pH-adjusting agents,sweetening agents, particulate abrasive materials, polymeric compounds,buffers and salts to buffer the pH and ionic strength of thecompositions, and mixtures thereof. Such ingredients typically andcollectively make-up less than 20% by weight of the composition, andpreferably, from 0.0 to 15% by weight, and most preferably, from 0.01 to12% by weight of the composition, including all ranges subsumed therein.

The oral care composition of this invention can be used in a method ofwhitening the teeth of an individual comprising applying the compositionto at least one surface of the teeth of the individual. Additionally,the oral care composition may be used in a method of remineralizing theteeth of an individual comprising applying the composition to at leastone surface of the teeth of the individual. The oral care composition ofthis invention may additionally or alternatively be for use as amedicament and/or used in the manufacture of a medicament for providingan oral care benefit as described herein, such as for increasing thewhiteness of the teeth of an individual.

Typically the composition will be packaged. In tooth paste or gel form,the composition may be packaged in a conventional plastic laminate,metal tube or a single compartment dispenser. The same may be applied todental surfaces by any physical means, such as a toothbrush, fingertipor by an applicator directly to the sensitive area. In liquid mouthwashform the composition may be packaged in a bottle, sachet or otherconvenient container.

The composition can be effective even when used in an individual's dailyoral hygiene routine. For example, the composition may be brushed ontothe teeth and/or be rinsed around the inside of the mouth of theindividual. The composition may, for example, be contacted with theteeth for a time period of one second to 20 hours. More preferably from10 s to 10 hours, more preferably still from 30 s to 1 hour and mostpreferably from 1 minute to 5 minutes. The composition may be useddaily, for example for use by an individual once, twice or three timesper day.

The following examples are provided to facilitate an understanding ofthe present invention. The examples are not provided to limit the scopeof the claims.

EXAMPLES

Oral care compositions consistent with this invention were preparedaccording to the formulations detailed in Table 1. All ingredients areexpressed by weight percent of the total formulation, and as level ofactive ingredient.

TABLE 1 Ingredient Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sorbitol60.0 55.0 65.0 50 35 PEG-1500 2.0 2.0 2.0 2.0 2.0 NaF 0.32 0.32 0.320.32 0.32 Sodium Saccharine 0.25 0.25 0.25 0.25 0.25 Sodium laurylsulfate 1.98 1.98 1.98 1.98 1.98 Flavor 1.00 1.00 1.00 1.00 1.00Abrasive silica 6.00 6.00 6.00 6.00 6.00 Thickening silica 7.00 7.007.00 7.00 — Sodium carboxymethyl cellulose 0.55 0.55 0.55 0.55 — Calciumsilicate hydrate — 5.00 5.00 10.00 30.00 Calcium silicate coatedtitanium 10 10 — 10.00 10.00 dioxide^(a) Water Balance Balance BalanceBalance Balance ^(a)Calcium silicate coated titanium dioxide wasprepared according to WO 2012/031785A

Example 1

This example demonstrates the improvement of tooth whitening effect byusing high refractive index composite particles in the presence ofcalcium silicate hydrate (CSH).

Preparation of Calcium Silicate Hydrate Powder

The calcium silicate hydrate (CSH) was prepared using a mixture ofcalcium hydroxide and sodium silicate in deionised water. The mixturewas formed with an initial Ca:Si ratio of 1:2. The mixture wascontinuously stirred at room temperature (25° C.). The pH of thereaction mixture was adjusted to and maintained around 11 usinghydrochloric acid. After stirring for 5 hours the reaction mixture wasfiltered and the cake washed three times with water before again beingfiltered. The filter cake was dried in an oven at 80° C. for 12 hours toyield the final CSH powder.

Methods

To investigate the whitening effect of the samples, the following invitro test was performed. Changes in whiteness just after the toothbrush with toothpaste in the morning is recorded as instant toothwhitening effect, and changes in whiteness after water brushing, whichmimics breakfast, is recorded as long-lasting tooth whitening effect.The measurement is carried out using a Konica Minolta-2600D colorimeter.The WIO index is an index which has been optimized specifically for theevaluation of whiteness in teeth (as described in Journal of Dentistry,volume 36, Supplement 1, 2008, pages 2 to 7).

The bovine tooth blocks were treated with different toothpaste viabrushing following the same protocol. At the start point, toothpaste wasmade into slurry by mixing toothpaste and water. The tooth blocks werebrushed with the fresh toothpaste slurry under a tooth brushing machineequipped with toothbrushes. The load of the tooth brushing was 170 g+/−5 g and the automatic brushing operated at a speed of 150 rpm. Afterbrushing for 1 min, the tooth blocks were rinsed with distilled waterand soaked in simulated oral fluid (SOF) under the condition of ashaking water bath at 37° C. and 60.0 rpm. After soaking for 3 to 4hours, the tooth blocks were brushed with water by machine using thesame procedure as brushing with toothpaste to mimic lunch. The toothblocks were soaked in SOF again for 3 to 4 hours before water brushingagain to mimic supper then the tooth blocks were brushed with toothpastefollowing the same procedure as in the first step. The tooth blocks werekept in SOF overnight in a shaking water bath at 37° C. to mimic oralenvironment. At the end point, the tooth blocks were water brushed againto mimic breakfast. These steps are considered as a whole treatmentcycle within one day. The tooth blocks were treated for 42 cycles intotal to mimic six weeks of twice daily tooth brushing. During theexperiment, the tooth colour was monitored at both start and end pointsevery day. After four weeks treatment, the tooth colour was monitoredevery two days. The changes in WIO values (ΔWIO) from baseline werecalculated and statistically analyzed.

Simulated oral fluid was made by combining the ingredients in Table 2:

TABLE 2 Ingredient Amount/g NaCl 16.07 NaHCO₃ 0.7 KCl 0.448 K₂HPO₃*H₂O3.27 MgCl₂*6H₂O 0.622 1M HCl 40 ml CaCl₂ 0.1998 Na₂SO₄ 0.1434 BufferAdjust pH to 7.0 Water Balance to 2 L

Results

The results of both instant whitening and long-lasting whitening effectafter certain period of time of treatment are summarized in Table 3 andTable 4, respectively (error represents 95% confidence interval forduplicate measurements).

TABLE 3 Change in WIO (Instant tooth whitening) Sample A Sample 1 Sample2 Sample 4 Sample 5 One week −1.33 ± 0.875 3.01 ± 1.272 4.62 ± 2.4132.21 ± 1.424 0.29 ± 1.108 Two weeks −0.61 ± 0.818 3.20 ± 1.064 5.70 ±1.292 3.58 ± 1.505 0.05 ± 1.465 Four weeks −0.90 ± 1.191 4.26 ± 2.2206.14 ± 1.765 4.85 ± 2.484 0.90 ± 1.150 Six weeks −0.49 ± 0.988 3.87 ±1.416 6.29 ± 1.083 5.66 ± 2.040 0.32 ± 1.089

TABLE 4 Change in WIO (Long-lasting tooth whitening) Sample A Sample 1Sample 2 Sample 4 Sample 5 One week −0.82 ± 0.866 −0.41 ± 0.771 1.65 ±1.354 0.12 ± 1.690 −0.42 ± 0.716 Two weeks −1.23 ± 0.891 −0.79 ± 1.3732.27 ± 1.527 0.417 ± 1.161  −1.02 ± 0.934 Four weeks −0.89 ± 1.221  0.15± 1.067 2.480 ± 0.927  1.03 ± 1.453  0.38 ± 1.535 Six weeks  0.06 ±0.983  0.66 ± 1.863 3.77 ± 1.494 2.04 ± 1.507  0.19 ± 0.948

Sample A is a comparative example using commercial toothpaste. In allcases, Samples 1, 2 and 4 showed significantly better instant toothwhitening effect than comparative Sample A. But Sample 5 comprising CSHand composite particles in a relative weight ratio of 3:1 showed noinstant tooth whitening effect.

In regards to long-lasting tooth whitening effect, Sample 2 and Sample 4comprising both CSH and composite particles had significantly betterperformance compared to Sample 1, Sample 5 and Sample A, which had nolong-lasting tooth whitening effect. Sample 3 comprising only CSH hadalso been compared to comparative Sample A, and showed no instant toothwhitening effect as shown in Table 5 (error represents 95% confidenceinterval for duplicate measurements).

TABLE 5 Change in WIO (instant tooth whitening) Sample A Sample 3 Afterone toothpaste brushing −0.04 ± 0.357 0.82 ± 1.140

After six weeks of twice daily brushing, SEM (Scanning ElectronMicroscopy) images of the enamel block surface were taken. Fromcorresponding cross-section SEM images, it appeared that the enamelblock treated with Sample 2 showed the formation of a new layer on thesurface while the one treated with Sample 1 did not have a new layerformed. Analysis using EDX (Energy Dispersive X-ray Spectroscopy)indentified the elements of Ti, Si, Ca and P within the new layer,indicating the deposition of composite particles on tooth surface.

Example 2

This example demonstrates the effect of relative weight ratio of calciumsilicate to composite particles on the tooth whitening effect.

Methods

To investigate the whitening effect of the samples, the following invitro test was performed. Changes in whiteness after water brushing,which mimics breakfast, is recorded as long-lasting tooth whiteningeffect.

The bovine tooth blocks were treated with different test samples viabrushing following the same protocol. At the start point, test sampleswere made into slurry by mixing with water. The tooth blocks werebrushed with the fresh slurry under a tooth brushing machine equippedwith toothbrushes. The load of the tooth brushing was 170 g +/−5 g andthe automatic brushing operated at a speed of 150 rpm. After brushingfor 1 min, the tooth blocks were rinsed with distilled water and soakedin SOF under the condition of a shaking water bath at 37° C. and 60.0rpm. After soaking for 3 to 4 hours, the tooth blocks were brushed withwater by machine for 1 min, then the tooth blocks were brushed againwith the slurry of the test samples using the same procedure as in thefirst step. The tooth blocks were soaked in SOF again for 3 to 4 hoursbefore brushing with water again to mimic supper then the tooth blockswere brushed with the slurry of the test samples following the sameprocedure as in the first step. The tooth blocks were kept in SOFovernight in a shaking water bath at 37° C. to mimic oral environment.At the end point, the tooth blocks were water brushed again to mimicbreakfast. These steps are considered as a whole treatment cycle withinone day. The tooth blocks were treated for 28 cycles in total to mimicfour weeks of three times daily tooth brushing. During the experiment,the tooth colour was monitored at the end point every day. The changesin WIO values from baseline were calculated and statistically analyzedin Table 7 (error represents 95% confidence interval for duplicatemeasurements).

TABLE 6 Ingredient Sample 6 Sample 7 Sample 8 Calcium silicate^(b) 5 1030 Calcium silicate 10 10 10 coated titanium dioxide^(a) GlycerinBalance Balance Balance ^(b)Commercially available calcium silicate(CaSiO₃) from P.Q. company (Sorbosil CA40)

TABLE 7 Change in WIO (Long-lasting tooth whitening) Sample 6 Sample 7Sample 8 One week 0.91 ± 2.555 −0.14 ± 1.518  −0.03 ± 0.767 Two weeks1.80 ± 4.187 1.93 ± 2.292 −0.11 ± 1.151 Four weeks 2.76 ± 3.995 2.98 ±2.603  0.46 ± 0.720

It can be seen that the relative weight ratio of calcium silicate tocomposite particles is important to the tooth whitening effect. Sample 6and Sample 7 having a smaller ratio of calcium silicate to compositeparticles showed significantly improved long-lasting tooth whiteningeffect, while there was no such effect observed in Sample 8.

1. An oral care composition comprising: a) calcium silicate ; and b)high refractive index composite particles; wherein the refractive indexof the composite particles is in the range from 1.9 to 4.0; and whereinthe calcium silicate and high refractive index composite particles arepresent in a weight ratio (a:b) of 1:10 to 2:1.
 2. The oral carecomposition according to claim 1, wherein the calcium silicate iscalcium silicate hydrate which comprises water of hydration in an amountof from 5 to 50% by weight of the calcium silicate hydrate.
 3. The oralcare composition according to claim 1, wherein the calcium silicate ispresent in an amount from 0.1 to 50% by weight of the composition. 4.The oral care composition according to claim 3, wherein the calciumsilicate is present in an amount from 1 to 20% by weight of thecomposition.
 5. The oral care composition according to claim 1, whereinthe refractive index of the composite particles is in the range from 2.5to 3.0.
 6. The oral care composition according to claim 1, wherein thehigh refractive index composite particles comprises a first componentcore comprising a metal salt, preferably the metal is selected fromzinc, titanium, zirconium or a mixture thereof, and a second componentcoating comprising the element calcium, and optionally, potassium,sodium, magnesium, aluminium or a mixture thereof.
 7. The oral carecomposition according to claim 6, wherein the metal salt is a metaloxide, preferably zinc oxide, titanium dioxide, zirconium dioxide or amixture thereof.
 8. The oral care composition according to claim 6,wherein the first component core of high refractive index compositeparticle is titanium dioxide.
 9. The oral care composition according toclaim 1, wherein the high refractive index composite particle istitanium dioxide coated with calcium silicate.
 10. The oral carecomposition according to claim 1, wherein the high refractive indexcomposite particle is present in an amount from 0.25 to 60% by weight ofthe composition.
 11. The oral care composition according to claim 10,wherein the high refractive index composite particle is present in anamount from 1 to 30% by weight of the composition.
 12. The oral carecomposition according to claim 1, wherein the relative weight ratio ofcalcium silicate to high refractive index composite particles rangesfrom 1:3 to 2:1.
 13. The oral care composition according to claim 1,wherein the composition is substantially free of phosphate source.
 14. Amethod for whitening the teeth of an individual comprising applying thecomposition as claimed in claim 1 to at least one surface of the teethof the individual.
 15. A process for manufacturing the oral carecomposition as claimed in claim 1 wherein the process comprises thesteps of: i) manufacturing high refractive index composite particles;ii) mixing the composite particles with calcium silicate to form theoral care composition.